More and more young women initiate intercourse in their teens; while increasing numbers experiment with contraception the pregnancy rate for sexually active adolescents remains intransigent. If populations at risk of ineffective use can be described by variables accessible at first clinic attendance, at first coitus or even before, programs could be designed to focus upon that subgroup components of service which may be identified with effective use. This study is an attempt to explore the correlates of effective and ineffective use of contraception, and non-use of contraception, in a population generally at high risk of unintended pregnancy: an inner city sample of black junior and senior high school males and females. It is planned in three sections designed to establish (1) the correlates of various levels of contraceptive use in a non-clinic population;(2) the correlates of effective and ineffective use in a clinic population,a selfselected subgroup of the school sample; and (3) methods to identify the service components of a delivery system associated with effective use. Step I of the study will utilize data from a questionnaire administered to 1,750 male and female inner city junior and senior high school students on their sexual knowledge, attitudes and behaviors before inauguration of an intensive pregnancy prevention program: the survey will be repeated and utilized to investigate relationships between changes in attitudes and changes in behaviors. A wide range of variables will be explored; using several multivariate techniques, especially discriminant analysis, correlates of use will be identified. Step II will utilize detailed sexualal histories collected at a clinic serving the same population to define use effectiveness by life table, retrospectively and prospectively, for individual contraceptive methods including the condom. Variables correlating with effective use will be assessed by mulltivariate techniques and tested as predictors of effective contraception on new patients admitted in the 3rd year of the study. Step III will utilize staff logs to determine all services actually received by students in the school and/or the clinic. Regression techniques including path analysis will be explored as methods for determining which components of the delivery system were highly associated with subsequent effective use.